The invention relates to "pressure cooking canners" and to means for facilitating cooling of containers therein after completion of a cooking cycle.
In many underdeveloped countries of the world, virtually none of the food produces is canned. Thus, while a sufficient total quantity of food may be grown within a country to last its inhabitants throughout the year, the actual consumable quantity of food may still not be sufficient to meet consumption needs. To alleviate such problems, canning centers may be set up various areas to accept food from large numbers of people and to can it in quantity on the premises. Pressure cookers used in such centers, while not usually as large as in commercial canning facilities, are large enough to economically handle sufficient quantities of food.
While pressure cookers for use in such canning centers are well known (see U.S. Pat. No. 2,555,230, which is incorporated herein by reference) there are several problems associated with their operation. Since the time required for the cooling cycle of a pressure cooker (retort) varies between twenty to 45 minutes depending upon the product being processed, there is a need to reduce the cooling time to enable more food to be processed within a given time (Attempted removal of product before the cooling cycle of the cooker has been completed -- i.e. before a zero pressure reading on the steam gauge -- could result in injury and or damage). If a reduction in retort pressure occurs prior to a corresponding reduction in pressure within the retort-enclosed food containers, the containers will break or food and liquid will leak from the containers. Some efforts to reduce the cooling cycle involve the application of pressurized air into the retort while the steam is condensing to maintain the pressure while the containers are being cooled. This, of course, requires the addition of an air compressor to the canning center.
According to the method and apparatus of the present invention, both of the above-mentioned problems inherent in prior art devices are avoided. According to the present invention the cooling cycle time is approximately 4 minutes and is usually less than 2 minutes. This results in a total cooling time before the cooker can be opened of approximately 1/10 that inherent in the prior art and increases the cooker production capacity by 25 - 40 percent. In addition, the need for an air compressor is eliminated since the pressure within the containers is effectively and reliably reduced prior to or at least contemporaneously with the reduction in pressure in the cooker. Accordingly, there is no need for an air compressor to maintain the pressure in the cooker at a particular level as in the past.
In prior art pressure cookers, as shown in U.S. Pat. No. 2,555,230, pressurized air is introduced into the retort and a fine mist of water is sprayed into the interior of the retort chamber from nozzles located on the cover thereof after the steam supply is terminated. The water delivery is always maintained in the form of a fine spray since slugs of cold water contacting the hot jars would be almost certain to cause breakage thereof.
According to the present invention, however, the water is delivered in direct streams rather than a spray. Further, the water streams are directed onto selected metal lids of the glass jars (food containers) within the retort. The water stream contacting the metal lid does three things: [1] the water stream quickly cools the jar lid and reduces the pressure within the jar faster than or at the same rate as the pressure is reduced around the jar to insure reliable fast sealing of the lid onto the jar; [2] the water absorbs sufficient heat from the lid to insure that it does not cause breakage of the jars when it subsequently flows down the jar sides to further cool the jars; and [3] a portion of the water vaporizes in the process thereby preventing too rapid a reduction in the retort pressure around the jars. Thus quick and safe removal of the containers from the retort is facilitated. After the jars are removed from the retort, they are further cooled to room temperature, such further cooling resulting in tight sealing of the lids on the jars. Thus it will be seen that the simple provision of a means for directing a stream of water on selected ones of the initially loose fitting metal tops of the jars within the retort eliminates the need for a compressor and reduces the time of the cooling cycle of the retort from 20 - 45 minutes to less than 4 minutes.
The preferred apparatus according to the present invention includes a means for positively locating the jars within the container and for positively locating the stream directing means with respect to the interior of the retort so that the streams will in fact be directed on various metal tops of the jars. It is not absolutely necessary that the top of every jar within the retort have a stream of water directed thereon. For example, when there are two layers of containers (which is a normal situation), the jars in the second layer need not have water directed on the tops thereof. Rather, the second layer jars merely receive the water dripping down from the top layer jars and the total cooling cycle for both layers of jars will still be no longer than the 4 minutes. Similarly, when in place of the normal sized (i.e. quart) jars that are used in the retort smaller sized (i.e. pint) jars are used, there will be more jars than there are water streams; thus only about 2/3 of the jars on the top layer will have a stream of water directed against their lid tops. With delivery of an adequate volume of water there is sufficient water vaporization, so that all the jars on the top layer will be cooled -- and similarly the jars on the second layer -- within 4 minutes.
The primary object of this invention is to provide an improved method and apparatus for food processing. This and other objects of the invention will become clear upon an inspection of the detailed description of the invention and the appended claims.